The two reactants shown below are combined to bring about a nucleophilic substitution reaction.

$C^c{H}_3{C}^b-=C^{a}Na+C{H}_3{H}^{C^e}{H}_2{C}^d{H}_2$Brlongrightarrow

f$.HBr$

i$.B{r}^{-}$

g$.C{H}_2=C{H}_2$

j$.N{a}^{+}$

h$.C{H}_{3}C-=C^{-}$

k$.C{H}_{3}C-=CH$

I. none

Which letter designates the electrophilic carbon at which substitution occurs? $($If no reaction occurs enter the letter corresponding to "none."$)$

Which letter corresponds to the leaving group?

Which letter designates the nucleophile?